Cooling of the electronics of an electrically operated device

ABSTRACT

A cooling system for cooling the components of an electrically driven rotating device, in which system the rotating part ( 4 ) of the device produces a current of a medium, such as air, the electric drive consisting of an electric motor ( 5 ) for rotating the device and an electronic control unit ( 6 ) controlling it, and which cooling system comprises at least one cooling element ( 62 ) for cooling the components. The cooling element ( 62 ) is disposed near the flow created by the rotating part ( 4 ) so that the heat produced by the components can be transmitted either directly and/or via a thermally conductive means to the current of cooling medium ( 63 ) created by the rotating device.

[0001] The present invention relates to a system for cooling the electronic components of an electrically operated rotating device as defined in the preamble of claim 1, in which system the rotating part of the device produces a flow of a medium, such as air.

[0002] For instance U.S. Pat. No. 4,618,806 presents an air impeller in which the rotor of a direct-current motor is combined with a bladed wheel so that the air impeller and the motor have a common frame and housing. In the air impeller according to the aforesaid patent, the stator of the d.c. motor imparts rotary motion to the bladed wheel and the rotor placed at its outer rim. In this patent, the air impeller is provided with a commutating circuit controlling the motor and placed in a separate casing near the outer edge of the air impeller.

[0003] A drawback with prior-art electrically operated air impellers as well as other rotating devices driven by an electric motor in which the motor is controlled by control electronics integrated with the device is that the electronics generate heat, which has to be removed to prevent overheating of and damage to the components.

[0004] The traditional solution for removing heat from electronics is to pass it to the external air outside the housing of the device or to blow cooling air into the device using a separate air impeller. The former alternative is not sufficiently effective in all situations, and the latter solution involves the problem of impurities gathering on the components as it allows dust and humidity carried by outer air to get into contact with the components. These reduce the service life of the device and impair its reliability. In addition, blowing air into the device requires a separate air impeller, which adds to the costs and vulnerability of the device.

[0005] The object of the present invention is to eliminate the drawbacks of prior-art solutions and to achieve a new type of cooling system for the electronics of an electrically operated rotating device. In the solution of the invention, a space for control electronics integrated with the housing of the rotating device is so de-signed that the heat produced by the components can be passed into the air flow generated by the rotating device.

[0006] The features characteristic of the cooling system of the invention are specified in the claims presented below.

[0007] The principal advantage of the invention is that it prevents the entry of dirt and humidity into the housing of the electronics. In addition, no separate air impeller is needed in the cooling system of the invention. The invention reduces the manufacturing costs of the device, simplifies its structure and improves its reliability.

[0008] In the following, the invention will be described in detail by the aid of an example with reference to the attached drawing, wherein FIG. 1 presents the cooling system of the invention in an axial impeller.

[0009] The figure shows an axial impeller that produces an air flow in the axial direction. The axial impeller has a plastic housing consisting of two halves, a front cover (not shown in the figure) and a back cover 2, fastened together e.g. by means of screws, the housing also serving as the frame of the impeller. Fitted in the front and back covers 1, 2 is a shaft journal 3, with a plastic impeller wheel 4 mounted on said shaft journal. The impeller wheel has in its center a hole 41 for a shaft and impeller blades 42 fitted around it between an inner cylindrical part 43 and a second, outer cylindrical annular part 44.

[0010] The impeller wheel 4 is rotated by an electric motor drive, the impeller wheel thus producing an air flow. The electric drive comprises a synchronous motor 5 and a frequency converter 6 or inverter controlling it and connected to a three-phase alternating-current network or a medium-level direct-current network, said frequency converter or inverter producing a sinusoidal output voltage with controlled frequency variation. The stator is mounted in the housing around the outer rim of the impeller wheel 4 and the rotor is integrated with the impeller wheel so that it consists of permanent magnets 51 fitted to the circumference of an outer annular part 44. The stator again consists of four stator segments placed symmetrically at even distances around the impeller wheel 4, each segment comprising a stator frame 52 and stator windings 54 wound in holes 53 at the curved inner rim of the stator segment. Each stator segment forms a segment of about 45° on the circumference of the impeller wheel 4.

[0011] The stator segments 52 have outer edges parallel to the vertical and horizontal edges of the impeller housing and extending only slightly outside the plane tangential to the outer rim of the rotor 4 to minimize the space required by the stator. In addition, the stator segments 52 may be provided with mounting holes to allow the stator segments to be fastened to mounting pins provided in the housing. Moreover, the housing part is provided with mounting pins 21 for attachment to the other housing part, and it has below the stator a space 23 for a frequency converter 6, said space being placed in the same plane perpendicular to the axial direction determined by the longitudinal axis, separated by a partition 22 from the two stator segments. Thus, the entire air impeller is integrated in the same housing 1, 2, which is very thin because all components are placed in the same plane perpendicular to the axial direction. In addition, the housing also functions as a mounting base, on which the various fixed components can be mounted and fastened as described above. It has fastening elements for the stator, for the bearings and the frequency converter or inverter. Moreover, the mounting base functions as a lead-through element for the motor conductors from the motor space into the housing of the frequency converter or inverter.

[0012] The frequency converter comprises a circuit board unit 61 fitted inside the housing part 2, in its lower part. On this circuit board are mounted the control electronics, e.g. power transistors, of the motor of the air impeller. Fitted against them in front of the circuit board unit 61 are cooling fins 62 in a separate housing part 24. The cooling fins 62 are placed beside the impeller wheel 4 between two stator segments 52. The heat produced by the electronic components is passed directly into the air gap 63 between the cooling fins 62 and the impeller wheel 4, and an air current flowing in the air gap cools the fins 62 and therefore the electronic components.

[0013] The heat produced by the electronic components can also be conducted into the stator segments 52 of the motor by fitting a cooling element into contact with the stator segment 52, which is cooled by the air flow. In this way, it is possible to reduce the size of the cooling element while simplifying the structure of the housing as well as that of the cooling element.

[0014] It is further possible to design a separate air channel into which the air flow generated by the impeller wheel is directed to cool the components.

[0015] It is obvious to the person skilled in the art that different embodiments of the invention are not limited to the example described above, but that they may be varied within the scope of the following claims. 

1. Cooling system for cooling the electronic components of an electrically driven rotating device, wherein the rotating part (4) of the device produces a flow of a medium, such as air, the electric drive consisting of an electric motor (5) for rotating the device and an electronic control unit (6) controlling it, and which cooling system comprises at least one cooling element (62) for cooling the components, characterized in that the cooling element (62) is disposed near the flow generated by the rotating part (4) so that the heat produced by the components can be transmitted either directly and/or via at least one thermally conductive means to the flow (63) of cooling medium produced by the rotating device.
 2. Cooling system as defined in claim 1, characterized in that the cooling element (62) has been fitted near the rotating part (4) so that they form a gap (63) for the flow of a flowing medium between them.
 3. Cooling system as defined in claim 1, characterized in that the cooling element and/or the components are fitted on a fixed part (5) of the device near the rotating part so that a gap for the flow of a flowing medium for cooling the components is formed between the fixed part and the rotating part.
 4. Cooling system as defined in claim 1, characterized in that the device is provided with a channel structure for passing the flow of a medium generated by the rotating part (4) to the vicinity of the components so that the heat produced by the components can be transmitted either directly and/or via a thermally conductive means to the flow of cooling medium produced by the rotating device.
 5. Cooling system as defined in claim 1 in a device having a housing (2), characterized in that it comprises inside the housing (2) a housing part (24) for a cooling element so that the cooling element (62) can be fitted near the flow generated by the rotating part (4) in such manner that the heat produced by the components can be transmitted either directly and/or via a thermally conductive means to the flow (63) of cooling medium produced by the rotating device. 